Over the past decade, the rapid increase in deployment of radiation portal monitors to address domestic and international security concerns has produced a significant demand for 3He gas. 3He is a stable isotope of helium that is used in the detection of neutron radiation as a counting gas in proportional counters. These detectors are not only used for security purposes but also found in large scale neutron science experiments as well as in nuclear scattering and imaging research fields. With the demand for 3He gas far outweighing the production, the US federal government began rationing 3He, only allocating it to certain groups or for certain purposes.
Plastic scintillators are traditionally utilized in radiation detection systems as a first line detection method. Their large volume, relatively low cost, and fast response times allow for their efficient use as gross counters, but they provide very limited spectroscopic information about the incident radiation. Due to their large hydrogen content, plastic scintillators are sensitive to fast neutron radiation via proton collisions that in turn have a thermalizing effect on the incident neutrons, allowing them to be detected by the currently employed 3He based proportional counters. Carboranes have traditionally been used as additives to increase boron content in plastic scintillators however, they are very expensive.